1. Field of the Invention
The present invention relates generally to a device for connecting an optical fiber in optical communication with an optoelectronic device and, more specifically, to a connector which permits a photosensitive device or light emitting device to be actively aligned with an optical fiber and permanently fixed in the aligned relationship in a quick and reliable manner.
2. Description of the Prior Art
In the field of optoelectronics, many situations arise where light signals must be coupled to electronic signals. For example, when optical fibers are used in a communication system, light signals passing through the optical fiber must be converted to electronic signals for use by associated equipment.
When light signals are coupled to electronic signals, the optical fiber must be located at a predetermined position relative to either a photosensitive device or a light emitting diode. The degree of permissible misalignment depends on the requirements of each application. One particularly stringent application is the coupling of an optical fiber to a PIN diode in a communication system in which data is transferred at gigabit rates. If the end of an optical fiber is misaligned in relation to the PIN diode, two deleterious conditions can adversely affect the transfer of information between light signals passing through the optical fiber and electronic equipment connected in signal communication with the PIN diode. If a portion of the light traveling through the optical fiber does not fall on the PIN diode, the efficiency of the device is diminished and the potential for lost signals is increased. Although this problem can adversely affect the accuracy of the data transfer between the optical fiber and the photosensitive device, an even more serious problem can be caused by a misalignment between the core of the optical fiber and the PIN diode. Since the PIN diode is typically incorporated within a integrated circuit that comprises many other components, such as photodiodes, capacitors, preamplifier circuits and other components, light which does not fall on the PIN diode will likely fall on other portions of the substrate of the integrated circuit. When this occurs, extra carriers are produced in those portions of the substrate and those carriers eventually migrate to the doped regions of the PIN diode. The time between the incidence of light falling on the non-PIN diode portions of the device and the migration of carriers to the PIN diode represents a delay that can improperly cause an electronic signal to be generated by the PIN diode at a time when no light signal is actually incident on the diode. Therefore, a misaligned connector can reduce the intensity of the intended electronic signal when a light signal is present in the optical fiber and can create false electronic signals at a time when no light signal is present in the optical fiber. For these reasons, high speed data communications systems require precise alignment between the optical signal carriers and the electronic components connected in signal communication with them.
In devices of the type described above, it is typical to employ active alignment techniques during the manufacture of the connector. In other words, after the optical fiber is firmly attached to the connector, the photosensitive device is placed proximate its final intended position and the electronic signal provided by the photosensitive device in response to a light signal through the fiber is monitored as the device is moved relative to the end of the optical fiber. When the electronic output signals from the photosensitive device indicate a proper alignment with the optical fiber, it is determined that the photosensitive device is in its proper position relative to both the optical fiber and the connector body. When this proper position is achieved, the photosensitive device can be rigidly and permanently attached to the connector body.
In certain applications of optoelectronic connectors, it is advantageous to use a zinc cast body for the connector because of its relatively low cost in comparison to a connector body made of machined stainless steel. However, the housing structure of a photosensitive device comprising a PIN diode in this application is made of Kovar and any material that is weld-compatible for welding to Kovar is likely to be incompatible for welding to the zinc cast body. If the photosensitive device is attached to the connector body with an epoxy, the time that is necessary to permit the epoxy to cure also increases the probability that the actively aligned components will be inadvertently misaligned. The additional care necessary to prevent misalignment during the time when the epoxy is curing could significantly increase the overall cost of the device.
Many different types of optoelectronics packages are well known to those skilled in the art. For example, U.S. Pat. No. 4,989,930, which issued to Nakagawa et al on Feb. 5, 1991, discloses a package that includes an optical semiconductor, an electronic cooling element carrying the optical semiconductor and electrically connected to one of the terminals of the semiconductor, a pair of transmission lines having distributed constant characteristics and an airtight vessel housing the optical semiconductor, the cooling element and the transmission lines. A grounding line of the transmission lines is connected between the terminal of the optical semiconductor and an external ground terminal fixed at the vessel. A signal line of the transmission line is connected between the other terminal of the optical semiconductor and an external signal terminal, whereby the stray capacitance of the cooling element is shorted by the distributed constant grounding line.
U.S. Pat. No. 4,988,159, which issued to Turner et al on Jan. 29, 1991, discloses an optoelectronic transducer which is connected with a fiber optic tail by providing a casing around the transducer. The casing has a flat wall. In addition, a termination body is provided on the fiber with a thin wall flange. The optical axes are aligned and the flange is laser welded to the casing.
U.S. Pat. No. 5,004,318, which issued to Ohashi on Apr. 2, 1991, describes an optical fiber switch that comprises a casing, a plurality of optical fibers attached to the casing and a vertically movable member that is disposed facing the ends of the optical fibers. The movable member is provided with a resilient portion provided at one end. A member, which is deformed to be contracted by supplying an electric power, is provided at the other end. The resilient portion can comprise a shaped memory alloy or a bimetal and is deformed to be contracted for causing the movable member to move vertically. The movable member can also comprise a plate that has an aperture for transmitting a light beam.